1. Field of the Invention
The present invention relates to a vehicle cooling system for removing heat generated by a vehicle unit (i.e., for cooling the vehicle unit). More particularly, the present invention relates to a vehicle cooling system configured and arranged to prevent thermal shock from occurring in a heat exchanger that is used to remove heat generated by a vehicle unit.
2. Background Information
In recent years, fuel cell automobiles have been developed which operate at high efficiencies and employ larger heat exchangers than gasoline engines due to the large quantity of heat emitted. A conventional vehicle cooling system of a fuel cell automobile is configured and arranged to circulate a coolant to a vehicle unit such as a fuel cell and other components to cool the vehicle unit. The coolant is circulated through a coolant circuit or route by a coolant pump. The coolant temperature increases when the coolant passes through the vehicle unit and the coolant releases heat as the coolant passes through a heat exchanger. A three-way valve is provided in the coolant circuit such that the three-way valve is switched between a heat exchanger position that directs the coolant through the heat exchanger and a bypass position that directs to coolant to bypass the heat exchanger. In the conventional vehicle cooling system, the temperature of the coolant at an outlet of the vehicle unit is detected and the three-way valve is switched to the heat exchanger position when the temperature of the coolant at the outlet of the vehicle unit is equal to or above a prescribed value. When the temperature of the coolant at the outlet of the vehicle unit is below the prescribed value, the three-way valve is switched to the bypass position so that the coolant bypasses the heat exchanger.
One known example of such conventional vehicle cooling system is disclosed in Japanese Laid-Open Patent Publication No. 2003-239745. The vehicle cooling system presented in this reference is provided with a thermostat that opens and closes automatically as a temperature of an engine coolant changes. The opening and closing of the thermostat controls an engine temperature by regulating a flow rate of coolant passing through a radiator (i.e., a heat exchanger).
A known example of a heat exchanger used in such conventional vehicle cooling system is disclosed in Japanese Laid-Open Patent Publication No. 2004-293982. This reference discloses a heat exchanger or a radiator having a pair of sheet plates arranged opposite to each other with a predetermined distance interposed therebetween at top and bottom positions of the radiator. A plurality of tubes and a plurality of corrugated fins are alternately arranged with a predetermined space interposed therebetween in a direction of the width of the radiator between the sheet plates.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved vehicle cooling system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.